P.M. Champion, D. Ionascu, F. Gruia , and X. Ye

Department of Physics and Center for Interdisciplinary Research on Complex Systems, Northeastern University, Boston, MA 02115 USA

This contribution reports on temperature dependent studies of the ultrafast kinetics and femtosecond coherence observed in heme proteins such as cytochrome c, its octapeptide, and myoglobin. Ultrafast studies of ligand binding in biological samples as a function of temperature have not previously been reported. Novel experimental techniques have been developed to carry out such studies so that the energy/entropy barriers associated with ultrafast recombination of the NO ligand can be determined for the first time. In addition, the coherence signals describing the low frequency vibrational excitations of biomolecules can be probed using similar experimental techniques. The low frequency modes, particularly one near 20 cm-1, are surprisingly robust and underdamped. It is possible that the 20 cm-1 mode is analogous to the "Boson" peak observed in biomolecules using other experimental methods [1] and suggested by theoretical calculations [2]. Acknowledgements: Supported by NSF 0211816 and the NIH DK 035090.

References

1.H. Leyser, W. Doster, and M. Diehl, Phys. Rev. Lett. 82, 2987 (1999).
2.Y. Seno and N. Go, J. Mol. Biol. 216, 111 (1990).